Engines operating on gaseous fuels, such as natural gas, may be supplied with a lean fuel mixture having a relatively high ratio of oxidizer to fuel. Conventional pre-chamber spark plugs may be used to enhance the lean flammability limits in lean burn engines. As one example, U.S. Pat. No. 7,922,551 describes a pre-chamber spark plug which reduces electrode erosion by spreading the discharge energy over a wider surface area via a swirling effect created by periphery holes in an end cap. However, in general there remain a number of unresolved disadvantages with the use of conventional pre-chamber spark plugs in lean burn engines and specifically as described in U.S. Pat. No. 7,922,551, as follow.
A first substantial disadvantage with conventional pre-chamber spark plugs may be that the configuration of the pre-combustion chamber does not adequately concentrate fuel at the spark gap region of the spark plug. One aspect of this disadvantage can be that the flow field forces within the spark gap region may be disorganized or even result in dead zones in which there is very little or no flow field. This can result in flame kernel quenching as there are no flow field forces to move the flame kernel away from the quenching surfaces.
A second substantial disadvantage with conventional pre-chamber spark plugs may be that the configuration of the pre-chamber promotes flame kernel development in proximity to flame quenching surfaces or promotes flame growth toward flame quenching surfaces.
A third substantial disadvantage with conventional pre-chamber spark plugs may be that the configuration of the pre-chamber may not mix in-filling streams with residual gases to sufficiently lower the temperature inside of the pre-chamber or the internal surface of the pre-chamber which may result in auto-ignition of the fuel-oxidizer mixture.
A fourth substantial disadvantage with conventional pre-chamber spark plugs may be that the configuration of the pre-chamber may not result in sufficiently fast burn rates with lean fuel mixtures resulting in deployment of flame jets into the main combustion chamber which by comparison with faster burn rates have lesser momentum.
These and other unresolved disadvantages with conventional pre-chamber spark plugs which can result in one or more slow and unstable combustion of fuel-oxidizer mixtures, flame quenching, auto-ignition, and decreased momentum of flame jets are addressed by the instant invention.